This invention claims the benefit of Japanese Patent Application No. 2000-126373, filed on Apr. 26, 2000, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a vehicle lamp for use in the illumination of a headlamp, fog lamp etc., and more particularly relates to a vehicle lamp that is thin and can form light distribution characteristics in a multi-reflex manner using an ellipse group reflector and a parabolic group reflector with high utilization efficiency of light emitted from a light source.
2. Description of the Related Art
FIG. 7 shows a conventional vehicle headlight 90 including a parabolic group reflecting surface such as a rotated parabolic surface. FIG. 8 shows another conventional vehicle headlight 80 including an ellipse group reflecting surface such as a rotated elliptic surface.
The conventional vehicle headlight 90 includes a first light source 91 such as a filament of an incandescent lamp, a parabolic group reflecting surface 92 such as a rotated parabolic surface having a focus located at the back of the first light source 91 and a rotation axis on an optical axis X (i.e., an illumination direction of the conventional headlight 90), a front lens 93 covering an aperture of the parabolic group reflecting surface 92 and having prismatic cuts 93a on its inner surface, and a shade 91a for formation of the low beam light distribution pattern. Since the first light source 91 is located in front of the focus of the parabolic group reflecting surface 92, light reflected by an upper half of the reflecting surface 92 is directed downward. The shade 91a covers a lower half of the light source 91 to prohibit unnecessary upwardly directed light rays from being reflected by a lower half of the parabolic group reflecting surface 92. A portion of upwardly directed light rays is required to illuminate the road side for and lighting road signs and/or pedestrians. In the case where the vehicle is driven in the left lane, the shape and location of the shade 91a are adjusted so as not to prohibit a predetermined portion of light rays which are to illuminate the upper left front view from the vehicle while prohibiting other portions of the upwardly directed light rays.
The vehicle headlight 90 further comprises a second light source 94 for the high beam light distribution pattern located substantially on the focus of the parabolic group reflecting surface 92. No shade is arranged for the second light source 94. A light distribution pattern of the vehicle headlight 90 is changed by switching the light source between the first light source 91 and the second light source 94.
The conventional vehicle headlight 80 can be referred to as a projection-type headlight 80 and comprises an ellipse group reflecting surface 82 such as a rotated elliptic surface having a first focus and a second focus, a light source 81 on the first focus, a shading plate 84 in the vicinity of the second focus, and a projection lens 83 having its focus in the vicinity of the second focus. The projection lens 83 has a convex lens on the front side, and a planar surface on the rear side relative to an optical axis X of the vehicle headlight 80. Light reflected by the ellipse group reflecting surface 82 converges to the second focus. An image of the luminous flux at the second focus is projected upside-down in the illumination direction X by the projection lens 83. On formation of low-beam mode light distribution pattern, the shading plate 84 prohibits a substantial lower half portion of luminous flux that converges at the second focus. The prohibited luminous flux would have been upwardly directed light rays after being projected by the projection lens 83. Accordingly, the image of luminous flux at the second focus has, in a cross section, a substantial upper chord located in an upper half of a circle. The image of the substantial upper chord is reversed upside-down when the luminous flux passes through the projection lens 83. Thus, the vehicle headlight 80 provides a low-beam mode light distribution pattern that does not include upwardly-directed light rays.
More specifically, the shading plate 84 prohibits not all of, but an unnecessary portion of, a lower half of the luminous flux at the second focus. A portion of the lower half of the luminous flux at the second focus which is to be upwardly directed light rays after passing through the projection lens 83 is permitted passageway to illuminate a road side. In the case where the vehicle is driven in the left lane, the shape and location of the shading plate 84 are adjusted so as not to prohibit a predetermined portion of the lower half of luminous flux at the second focus that illuminates the upper left front view from the vehicle after passing through the projection lens 83, while prohibiting other portions of the lower half of luminous flux at the second focus. When the vehicle headlight 80 changes its light distribution pattern mode from low-beam to high-beam, the shading plate 84 is moved away from luminous flux converged at the second focus. In the conventional projection-type vehicle headlight 80, the shading plate 84 is located perpendicular to the optical axis X of the ellipse group reflecting surface 82.
Conventional vehicle headlights 90 and 80 have at least the following problems. First, the conventional vehicle headlights 90 and 80 respectively include a shade 91a and shading plate 84. The shade 91a and shading plate 84 respectively prohibit substantially half of the total light amount emitted from the first light source 91 and light source 81. Therefore, utilization efficiency of light emitted from the first light source 91 and light source 81 in low-beam mode is small, giving the impression that the vehicle headlights 90 and 80 are dark in comparison with light amounts emitted from the first light source 91 and light source 81, respectively.
The conventional vehicle headlights 90 and 80 also have restricted design flexibility. From a view point of automobile body design, it is preferable for the vehicle headlights 90 and 80 to have a large width and a small height in front view. In the conventional vehicle headlight 80, it is possible to have a smaller height. However, it is difficult, if not impossible, to have a larger width. In the conventional vehicle headlight 90, there exits a limit to which the height of the headlight can be reduced while satisfying functional requirements of the headlight. Reduction of the height also results in decreasing utilization efficiency of lumen output by the parabolic group reflecting surface 92. Accordingly, it is difficult to greatly change the current design of the conventional vehicle headlights 90 and 80.
In order to solve the aforementioned problems in the related art, in the present invention, a vehicle light can include a light source, at least a pair of ellipse group reflecting surfaces configured to symmetrically surround the light source. Each ellipse group reflecting surface can have a first focus located on the light source, and can have a longitudinal axis that is perpendicular to an optical axis of the vehicle light. The same number of parabolic group reflecting surfaces as ellipse group reflecting surfaces can be located substantially linearly so as to cause light rays to be directed in predetermined directions from the vehicle light. Each parabolic group reflecting surface can have a focus located substantially on the second focus of one of the ellipse group reflecting surfaces, and can have an optical axis that is substantially parallel to the optical axis of the vehicle light. A shading plate can be located in the vicinity of the second focus of one of the ellipse group reflecting surfaces for providing a predetermined shape to luminous flux that converges from the ellipse group reflecting surface.
In accordance with another aspect of the invention, a vehicle lamp having a multi-reflex optical system and an optical axis can include a light source, an ellipse group reflecting portion configured to substantially surround the light source, a parabolic group reflecting portion having a focus on the second focus of the ellipse group reflecting portion, and a shade located in the vicinity of a second focus of the ellipse group reflecting portion to provide a predetermined shape to luminous flux directed from the ellipse group reflecting portion. The ellipse group reflecting portion can be substantially symmetrical relative to the light source and can have a first focus in the vicinity of the light source and a second focus. A longitudinal axis of the ellipse group reflecting portion is preferably substantially perpendicular to the optical axis of the vehicle lamp, and a longitudinal axis of the parabolic group reflecting portion can be substantially parallel to the optical axis of the vehicle lamp.
In accordance with yet another aspect of the invention, a vehicle lamp can include a light source, an ellipse group reflecting portion configured to substantially surround the light source, a parabolic group reflecting portion having a focus on the second focus of the ellipse group reflecting portion, and means located in the vicinity of the second focus of the ellipse group reflecting portion for providing a predetermined shape to luminous flux directed from the ellipse group reflecting portion. The means for providing a predetermined shape can include a shade, a movable shade, and/or other mechanism for shaping luminous flux in a predetermined shape. The ellipse group reflecting portion can be located substantially within the parabolic group reflecting portion and form a chamber from which light from the light source is directed to the parabolic group reflecting portion such that light is then directed parallel to the optical axis of the vehicle lamp.